Flotation method and apparatus



Oct. 18, 1927. 1,646,019

D. L. FORRESTER FLOTATION METHOD AND APPARATUS Filed July 29. 1925 mill.

INVENTOR David Lawzon Frresi'cr MZJI LM ATTORNEY Patented Oct. 18, 1927.

UNITED STATES DAVID LAWTON FORRESTER, OF GLOBE, ARIZQNA.

FLOTATION METHOD AND APPARATUS.

Application filed July 29,

My invention relates to improvements in apparatus for the concentrationof the values from ores or other substances by what is commonly known asthe flotation process, in which the ores or other substances aresubjected to aeration in an aqueous separating medium in the presence ofsuitable agents for the formation of a froth containing the valuableportions of said ores or other substances, and thereby separating saidvalues from the barren or rocky constituents thereof. An inherentcharacteristic of the a paratus is the novel method of producing tidenecessary aeration of the pulp.

The object of the present invention is to provide certain improvementsin flotation apparatus which by the simplicity of construction reduce.the cost of production, 1nstallation and operation.

The principle of operation and novel features of the invention will bebetter understood' from the following description taken in conjunctionwith the accompanying drawing illustrating the preferred form of aflotation cell-embodying the invention.

In this drawing:

Fig. 1 is a longitudinal section of the flotation cell, taken on lineAA, Fig. 2. I

Fig. 2 is a transverse section of the flotation cell, taken on line -BB,Fig. 1.

Referring now particularly to the accompanying drawing, the apparatustherein illustrated is a flotation cell of the pneumatic type. Asrepresented in the drawing the cell has a sloping bottom 1, and upwardlyand outwardly inclined side Walls 2, at the 'upper end of which areprovided concentrate launders 3. The vertical end walls 4 and 5 completethe cell roper.

Within this cell are ongitudinal partitions 6 and 7, which define anagitation chamber. The best results so far secured have been by the useof an agitation chain ber larger in its upper portion than in its lowerportion, and consequently the upper partitions 6 are shown more widelyspaced than the lower partitions 7, there thus being an abrupt increasein the cross section of the agitation chamber, as clearly indicated inFig. 2. The partitions 6 extend well above the froth overflow lips 9 andthe space between them is open to the atmosphere. The partitions 6 areprovided with slots or holes, arranged in a series extending the entirelength of the artitions, and below the normal level of the pulp in the1925. Serial No. 46,783.

tank. These openings are to permit the passage of the aerated pulp (ascontradis tinguished from froth) from the agitation chamber between thepartitions 6 to the extremely large as compared with the openings of theporous media usually employed, and large as compared with the openingsemployed in those apparatuses heretofore proposed in which it isintended to inject jets ,of air under relatively high pressure.

The pulp, containing suitable flotation agents, may enter through thefeed compartment 10, or it may be introduced directly into the agitationchamber.

The discharge end of the cell is provided with'the usual type of weirdischarge 11, which is provided with means 12, for. regulating the pulplevel in the cell.

The introduction of air through the relatively large openings of'thepipes 8 produces a disturbance of the pulp in the agitation chamber thatresults in a rapid circulation of the pulp from the agitation chamberthrough restricted communications into the separation chamber anddownwards, re-'entering the agitation chamber in part and in partpassing on into the tailing discharge. The air discharges from the pipes8 in bubbles which are very large relatively to the bubbles in theresulting froth. The circulating pulp while tending to reenter theagitation chamber moves in directions due to its path of circulation andthe direction induced by the position of lower partitions 7. Thecirculating pulp comes in contact with the entering air while moving incross currents to that of the entering air and an agitation is sofurther induced. The tendency of the large bubbles is to raise thecolumn of pulp through which they are passing and by the crosscirculation of pulp they are sheared or pinched so as to producesubdivision or dissemination of the relatively large bubbles and theirdispersion in the pulp in the size desired. The pulp passing into theseparation chamber thus carries wit it a considerable portion of the airintroduced into the agitation chamber. This air having been relativelyfinely divided is in a suitable agitation chamber.

condition to produce an eifective froth onthe surface of the pulp in theseparation chamber.

, The device thus involves an important operative characteristic, whichis that air dis- ,charged at a rapid rate and in relatively largebubbles not only produces the circula- 'tion,.but produces within thebody of the from the gangue. The circulation is induced in the firstinstance by large bubbles of air discharged below the entrance of thechamber, at points relatively remote from the zone of violent agitation,the fine bubbles developed by the agitation are fed away to the lateralchambers in which the flotation separation by the resulting frothoccurs. The abrupt widening of the agitation chamber, at a pointsubstantially below the surface of'the pulp, improves the result becauseof the improved agitation secured.

The advantages of the apparatus of this invention are apparent. Nomechanical propellers or rotors are used to aerate the pulp and noporous medium of any kind is used for introducing air into the pulp.Thus the power for, and the wear and tear incident to the operation ofmachinery usually employed to aerate the pulp, and also the powerrequired to force air through, and the wear and tear incident to theporous medium usually employed has been entirely done away with in theoperation of the apparatus of this invention. As the size of theopenings in the pipes for air introduction into the pulp in theapparatus of this invention is large compared with the openings of theporous medium usually employed, the power required is much reduced overthat required by apparatus employing porous media. The apparatus of thisinvention has the further vantage over those employing porous media thatthe openings for air introduction do not become clogged as do the openings in a porous medium. Blankets or other porous media becomeespecially troublesome when lime is being used as a reagent, or when theore being treated is courseor of high specific gravity.

While the apparatus illustrated and described has been foundparticularly advantageous, yet it will be understood that variations andmodifications may be made therein without departing from the spirit ofthis invention.

I claim:

1. The method of concentrating ores by flotation which consists inaerating a pulp bydischarging air in large bubbles into the From thesides of this.

same at a substantial depth below the surface-thereof, directingcoacting currents of pulp against said bubbles adjacent their point ofentry, and causing circulation of the pulp through zones,'one of violentagitation produced by the air and the other of approximate quiescence,the pulp in both zones being under normal atmospheric pressure;isolating said Zones from each other and confining the flow from thefirst to the second to a restricted approximately horizontal path belowthe surface of the pulp, and removing .mineral-bearing froth from thezone of quiescence.

2. The method of concentrating ores by flotation which consists inintroducing large bubbles of air into and below the surface of a pulpfreely open to the atmosphere; causing a circulation of the pulp to beset up;

bringing the circulating pulp in directly incombination means forming apulp container having an agitation chamber and a frothseparating chamberwith froth overflow;

means for permitting the circulation of pulp from one chamber toanother, comprising unrestricted communlcation between said chambers inthe lower portion of the container through opposite sides of the agitating chamber, said agitating chamber being internally substantiallyunobstructed at the level of said communication, and agitationconfiningmeans offering restricted commu nication at a higher level, but whollybeneath the pulp level, both chambers being freelyopen to theatmosphere; and means for creating a circulation of the pulp upwardlythrough the agitation chamber and returning through said unrestrictedcommunication in the lower portion of the container comprising an airpipe discharging air in large bubbles directly into the pulp below thepoint of unrestricted communication of the chambers. i

at. A flotation concentrator comprising in combination a tank for theretention of a body of pulp, having means for froth discharge; apartition structure defining within the tank an agitation chamber,'unrestrictedly open at opposite sides at its bot tom to the tank and atits top freely open to the atmosphere, said agitation chamber beingsubstantially unobstructed at the level of the pulp inflow, there alsobeing restricted openings through said partition structure wholly belowthe pulp level; and means for creating a circulation of the air and pulpupwardly through the agitation chamber sizes.

5. A flotation concentrator comprising in combination a tank havingfroth overflows; a partition structure extending above said overflows,and defining within the tank an agitation chamber unrestrictedly open'at opposite sides at its bottom to the tank and at its top freely opento the atmosphere, said agitation chamber being substantiallyunobstructed at the level of the pulp inflow,

there also being restricted openings through til said partitionstructure wholly below the pulp level; and means for creating acirculation of the pulp upwardly in said agitation chamber and outtherefrom through said restricted openings, comprising means dischargingair in large bubbles directly into the pulp below the lower end of theagitation chamber.

6. A flotation concentrator comprising in combination a tank havingfroth overflows; a partition structure extending above said overflows,and defining within the tank an agitation chamber open at its top freelyto the atmosphere and at its bottom to the interior of the tank, saidchamber being relatively narrow at its lower end and abruptly enlargedat a substantial distance below said overflows, there being restrictedopenings through said partition structure below the pulp level and abovethe level of such enlargement; and means for discharging air in largebubbles directly into the pulp below the lower end of the agitationchamber.

7 A flotation concentrator, comprising in combination an elongated tankhaving lateral froth overflows; a pair of longitudinal partitions withinsaid tank and near the bot-- tom thereof, the space between saidpartitions being freely open around the lower edges of the partitions tothe remainder of the interior of the tank; a pair of more widely spacedpartitions extending from approximately the upper margin of the lowerpartitions to a point above the level of the froth overflows, the lastnamed partitions being provided with openings below the pulp level inthe tank through which aerated pulp may pass; and means for dischargingair in relatively large bubbles below the lower ends of and between thefirst-named partitions and substantially throughout the entire length ofthe tank.

8. The method'of concentrating ores by flotation which consists inaerating a pulp by discharging air in large bubbles into the same at asubstantial depth below the surface thereof in quantity sufiicient tomaintain circulative travel through zones, one of violent circulativeagitation and the other of approximate quiescence, the circulativetravel being wholly below the pulp level and that from the agitatingzone to the zone of quiescence being confined to a restrictedapproximately horizontal path, and removing mineral-bearing froth fromthe zone of quiescence.

9. The method of concentrating ores by flotation which consists in'discharging air in large bubbles and in relatively large volumes into abody of pulp in the lower portion thereof and inducing simultaneousagitation and upward flow of pulp and air through an agitating zone, theupper portion of said zone being expanded to decrease the rate of upwardflow of said pulp and air and cause agitative circulation therein, andcausing flow of said ulp laterally through communications who y belowthe pulp level into a separation zone, and collecting the resultantfroth.

10. Themethod of concentrating ores by flotation which consists inproviding an agitating zone and a zone of approximate qu1escence in abody of pulp, the pulp in both zones being under normal atmosphericpressure, aerating the pulp by discharging air in large bubbles intothe'same at a substantial depth below the surface thereof in the firstzone, causing agitative circulation therein, and inducing a flow of pulpfrom the second zone into the first zone in the vicinity of the point ofentry of the air and causing flow of the air andpulp through the firstzone accompanied by agitative circulation therein and thence into thesecond zone, the flow-from the first to the second zone being confinedto a restricted, approximately horizontal path wholly below the surfaceof the pulp, and removing mineral-bearing froth from the zone ofquiescence.

In testimony whereof, I have signedmy name to this specification this21st day of July, 1925.

DAVID LAWTON FORRESTER.

